The present invention relates, in general, to semiconductor packages, and more particularly, to semiconductor packages having high electrical breakdown resistance.
Many semiconductor packages include a heatsink which is thermally coupled to a semiconductor die for the dissipation of heat during the operation of the semiconductor device. At times, these heatsinks are also electrically connected to the semiconductor die through a die flag. To protect the semiconductor device from high current flow due to high voltage potentials, it is necessary to electrically insulate the heatsink of the semiconductor device.
One method relies on insulating the heatsink when it is mounted onto a circuit board as part of a larger system. To help cool each component in a system, the heatsink of each package is mounted onto a larger heatsink which dissipates the heat generated by the entire system. To electrically insulate the heatsink of the package from the heatsink of the system, the package is coated with grease and mounted onto a non-conductive pad with an insulated screw. This method adds cost to the system and reduces the efficiency of the heatsink to dissipate heat.
Some other previously known techniques which insulate the heatsink of the package, rely on forming a layer of molding compound between the heatsink and semiconductor die or encapsulate both the heatsink and semiconductor die in molding compound. The mold compound used must be thermally conductive which is more expensive than the standard mold compound used in the industry. Both of these techniques are adequate for insulating the heatsink of a semiconductor package, but do so with added assembly cost.
Accordingly, it would be advantageous to have a method for insulating the heatsink of a semiconductor package so that the package can be mounted into a system and offer protection from currents which can result due to high voltage potentials. It would be of further advantage to provide a method that offers the flexibility to perform the method during any step of the assembly process and do so while adding nominal cost to the final product. It would be of even further advantage if the method did not require any environmentally hazardous chemicals or produce any by-products which must be disposed of. It would also be advantageous if this method could also be used to electrically isolate portions of a semiconductor device from each other.